This project will develop a simple test for noninvasive diagnosis of active Helicobacter pylori infection in the stomach based on measuring ammonia in patients' breath. A novel highly sensitive optical technique will be used to measure breath ammonia, leading to an inexpensive diagnostic procedure that can be conducted in any general practitioner's office. An improved method of detecting gastric H. pylori is of clinical significance because the organism causes most notably peptide ulcers as well as other gastrointestinal diseases including cancers. The new breath ammonia sensing method will be useful for diagnosis of infected patients, as well as follow-up determinations of infectious status after therapy. The research will demonstrate the feasibility of the ammonia-based technique in Phase I through a limited clinical trial using current research instrumentation. This effort will include investigations characterizing and improving the sensing method and qualifying the clinical protocol. Subsequent Phase II research will refine the sensing system building clinical level prototype instruments. Expanded patient trials will be conducted to confirm the clinical efficacy of the protocol and improved diagnostic system. PROPOSED COMMERCIAL APPLICATIONS: The sensing technique is primarily designed for clinical diagnosis of gastric H. pylori and related disease applications. It is also applicable towards ammonia detection in context of their disease states associated with elevated ammonia, e.g. end-stage renal failure. As a high-sensitivity ammonia detection system, the technology is valuable for sensing ammonia in industrial and food industry applications.